Seatbelt pretensioning retractor assembly

ABSTRACT

A seatbelt pretensioning retractor assembly for use in a passenger vehicle is provided. The pretensioning assembly includes a tube in fluid communication with a gas generator and a driving element disposed therein that travels in a first direction in response to actuation of the gas generator. The driving element includes a plastically deformable polymer rod with a recessed portion. A stopper is coupled to an end portion of the plastically deformable polymer rod. A seal member is disposed between the gas generator and the stopper. The tube includes a projection extending within the tube adjacent to the exit to define a constriction portion. The constriction portion is sized to permit the recessed portion of the plastically deformable polymer rod to pass therethrough while preventing the stopper from passing therethrough.

TECHNICAL FIELD

The technical field relates generally to seatbelt restraint devices forrestraining an occupant of a vehicle, and more particularly, to devicesfor pretensioning a seatbelt.

BACKGROUND

Seatbelt restraint systems for restraining an occupant in a vehicle seatplay an important role in reducing occupant injury in vehicle crashsituations. Seatbelt restraint systems of the conventional so-called“3-point” variety commonly have a lap belt section extending across theseat occupant's pelvis and a shoulder belt section crossing the uppertorso, which are fastened together or are formed by a continuous lengthof seatbelt webbing. The lap and shoulder belt sections are connected tothe vehicle structure by anchorages. A belt retractor is typicallyprovided to store belt webbing and may further act to manage belttension loads in a crash situation. Seatbelt restraint systems which aremanually deployed by the occupant (so-called “active” types) alsotypically include a buckle attached to the vehicle body structure by ananchorage. A latch plate attached to the belt webbing is received by thebuckle to allow the belt system to be fastened for enabling restraint,and unfastened to allow entrance and egress from the vehicle. Seatbeltsystems, when deployed, effectively restrain the occupant during acollision.

OEM vehicle manufacturers often provide seatbelt restraint systems withpretensioning devices, which tension the seatbelt either during animpact of the vehicle or even prior to impact (also known as a“pre-pretensioner”) to enhance occupant restraint performance. Thepretensioner takes out slack in the webbing and permits the beltrestraint system to couple with the occupant early in the crashsequence. One type of pretensioner acts on the webbing retractor totension the belt. Various designs of retractor pretensioners presentlyexist, including a type known as a roto-pretensioner that incorporates agas generator for generating a pyrotechnic charge. Examples of suchroto-pretensioners are described in U.S. Pat. No. 5,881,962, filed Apr.11, 1995, U.S. Patent Application Publication No. 2006/0243843, filedApr. 27, 2005, U.S. Patent Application Publication No. 2012/0006925,filed Jul. 6, 2010, and U.S. Pat. No. 7,988,084, filed Aug. 2, 2011,which are commonly owned by the assignee of the present application andare hereby incorporated by reference in their entirety for all purposes.Generally, ignition of the pyrotechnic charge or other combustiblematerial creates gas pressure in a chamber having a piston to impartmotion upon a driving element such as a piston, rack and pinion, orseries of balls disposed in a pretensioner tube, which engage with andwind a retractor spool sprocket to retract the webbing.

One issue with pretensioners using a series of metallic balls is theweight of the series of balls required for a full pretensioning stroke,as well as the corresponding cost of supplying multiple metallic ballswith strict tolerances. Further, for pretensioners using a series ofmetallic balls, or rack and pinion based systems, is the need for asynchronizing or clutch feature to ensure that the series of balls orpinion sufficiently engage the retractor spool sprocket.

Another issue with pretensioners is known as a low resistance condition,where the driving elements will reach an end of stroke withoutexperience substantial resistance. This can occur if there is excessiveslack in the seatbelt webbing. In these cases, the low resistanceresults in a lower amount of backpressure from the driving elements. Thebackpressure is produced by the engagement between the driving elementsand the sprocket, so lower backpressure reduces the pressure on asealing element that trails the driving elements. Reduced pressure onthe sealing elements reduces the amount that the sealing element iscompressed circumferentially. Reduced sealing ability can cause gas toleak from the tube around the series of balls.

A further issue with pretensioners is the need to maintain the retractorand the seatbelt webbing in a locked condition at the end of thepretensioning stroke. When the retractor spool does not remain locked,payback can occur which allows the seatbelt to unspool and reintroduceslack in the seatbelt. One method for maintaining the locked positionincludes maintaining pressure from the gas generator beyond the amountneeded for the pretensioning stroke. However, this adds weight and cost.

BRIEF SUMMARY

Seatbelt pretensioning retractor assemblies for use in a passengervehicle are provided herein. In an exemplary embodiment, a seatbeltpretensioning retractor assembly includes a housing that is adapted forbeing mounted to a vehicle structure. The housing has an interiorcavity. A tube with an arcuate and curved shape has a first end forfluid communication with a gas generator and a second end in fluidcommunication with the interior cavity of the housing. A sprocket isrotatably mounted to the housing and fixedly coupled to a spindle thatis adapted for taking up seatbelt webbing during pretensioning. Thesprocket has a plurality of vanes. A driving element includes aplastically deformable polymer rod that is configured to extend in alongitudinal direction and has a recessed portion defining a recess thatextends generally in the longitudinal direction. The plasticallydeformable polymer rod is disposed within the tube and is translatablethrough the tube in a first direction toward the sprocket in response toan actuation by the gas generator. A stopper is coupled to an endportion of the plastically deformable polymer rod. A seal member isdisposed between the gas generator and the stopper. The tube includes aprojection extending inside the tube adjacent to the exit to define aconstriction portion. The constriction portion has an opening dimensionsmaller than an inside dimension of adjacent portions of the tube. Therecess is aligned with the projection in the first direction and theconstriction portion is sized to permit the recessed portion of theplastically deformable polymer rod to pass therethrough while preventingthe stopper from passing therethrough.

In another exemplary embodiment, a seatbelt pretensioning retractorassembly for use in a passenger vehicle is provided. The seatbeltpretensioning retractor assembly includes a housing adapted for beingmounted to a vehicle structure and has an interior cavity. A tube has anarcuate and curved shape having a first end for fluid communication witha gas generator and a second end in fluid communication with theinterior cavity of the housing. A sprocket is rotatably mounted to thehousing and fixedly coupled to a spindle adapted for taking up seatbeltwebbing during Pretensioning. The sprocket has a plurality of vanes. Adriving element includes a plastically deformable polymer rod configuredto extend in a longitudinal direction and has a recessed portiondefining a recess that extends generally in the longitudinal direction.A recessed section extends in the longitudinal direction on a sideopposite the recessed portion. The plastically deformable polymer rod isdisposed within the tube and is translatable through the tube in a firstdirection toward the sprocket in response to an actuation by the gasgenerator. A seal member is disposed between the gas generator and theplastically deformable polymer rod. The tube includes a projectionextending within the tube adjacent to the exit to define a constrictionportion that has an opening dimension smaller than an inside dimensionof adjacent portions of the tube. The recess, which is defined by therecessed portion in the plastically deformable polymer rod, is alignedwith the projection in the first direction and the constriction portionis sized to permit the recessed portion of the plastically deformablepolymer rod to pass therethrough. The recessed section is sized suchthat a thickness of the plastically deformable polymer rod definednormal to the recessed section is less than a width of the plasticallydeformable polymer rod defined normal to the thickness to facilitatebending of the plastically deformable polymer rod through the tubeduring translation in the first direction.

Further objects, features, and advantages of the invention will becomeapparent to those skilled in the art to which the present inventionrelates from consideration of the following description and the appendedclaims, taken in conjunction with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is perspective view of an occupant restraint system in accordancewith an exemplary embodiment;

FIG. 2 is a perspective view of the occupant restraint system withvarious components removed to show a seatbelt pretensioning retractorassembly in accordance with an exemplary embodiment;

FIG. 3 is a perspective view of the seatbelt pretensioning retractorassembly in accordance with an exemplary embodiment;

FIG. 4 is a cut-away view of the seatbelt pretensioning retractorassembly illustrating a tube, a plastically deformable polymer rod, anda sprocket in a non-actuated position in accordance with an exemplaryembodiment;

FIG. 5 is a side cut-away view of the plastically deformable polymer rodand a stopper in accordance with an exemplary embodiment;

FIG. 6 is a side cut-away view of the plastically deformable polymer rodand the stopper in accordance with another exemplary embodiment;

FIG. 7 is a plan view of the sprocket having a plurality of vanes inaccordance with an exemplary embodiment;

FIG. 8 is a side view of the sprocket in accordance with an exemplaryembodiment;

FIG. 9 is a partial view of the sprocket illustrating the shape of thevanes in accordance with an exemplary embodiment;

FIG. 10 is a cross-sectional view of a gas generator, a seal, thestopper, and the plastically deformable polymer rod of the seatbeltpretensioning retractor assembly in the non-actuated position inaccordance with an exemplary embodiment;

FIG. 11 is a cross-sectional view of the seatbelt pretensioningretractor assembly in an actuated position in accordance with anexemplary embodiment;

FIG. 12 is a partial exploded perspective view of the tube, theplastically deformable polymer rod, and the stopper in accordance withan exemplary embodiment;

FIGS. 13A-13E are cross-sectional views of various embodiments of theplastically deformable polymer rod illustrated in FIG. 5 along line13-13;

FIG. 14 is a cut-away perspective view of a constriction portion in thetube of the seatbelt pretensioning retractor assembly in accordance withan exemplary embodiment;

FIG. 15 is a cross-sectional view of another embodiment of theconstriction portion;

FIG. 16 is a cross-sectional view of another embodiment of theconstriction portion;

FIG. 17 is a cross-sectional view of another embodiment of theconstriction portion;

FIG. 18 is a cut-away view of the seatbelt pretensioning retractorassembly illustrating a tube, a plastically deformable polymer rod, anda sprocket in a non-actuated position in accordance with anotherexemplary embodiment;

FIG. 19 is a side cut-away view of the plastically deformable polymerrod and a stopper in accordance with another exemplary embodiment;

FIG. 20 is a plan view of the plastically deformable polymer rod and astopper depicted in FIG. 19;

FIGS. 21A-21C are cross-sectional views of the plastically deformablepolymer rod depicted in FIG. 20; and

FIG. 21D is an enlarged view of a portion of the plastically deformablepolymer rod depicted in FIG. 19.

It should be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

DETAILED DESCRIPTION OF THE INVENTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure or its application or uses.

Referring now to the drawings, FIG. 1 shows a vehicle seat 10 and aseatbelt assembly 12 in accordance with an exemplary embodiment. Theseatbelt assembly 12 includes a seatbelt webbing 14 having a shoulderbelt portion 16 extending from an upper guide loop or anchorage 18 to alatch plate 20 and a lap belt portion 22 extending from the latch plate20 to an anchorage 24. The latch plate 20 can include a loop portion 26through which the seatbelt webbing 14 extends. The latch plate 20 isable to be inserted into a seatbelt buckle 28 to lock and unlock theseatbelt assembly 12. A seatbelt buckle cable 30, either directly or incooperation with other components, secures the seatbelt buckle 28 to aportion 31 of the vehicle structure (e.g., vehicle frame). It will beappreciated that other manners of attaching the seatbelt webbing 14 tovehicle could also be used, including variations on the latch plate 20and the seatbelt buckle 28 and their attachments to the seatbelt webbing14 and associated vehicle structure.

The seatbelt webbing 14 is able to pay-out from a seatbelt pretensioningretractor assembly or retractor assembly 32 (shown in FIGS. 2 and 3),which is located within the vehicle seat 10 (in an integrated structuralseat design) or is coupled structurally to the vehicle body, so that theeffective length of the seatbelt webbing 14 is adjustable. When thelatch plate 20 has been fastened to the seatbelt buckle 28, the seatbeltassembly 12 defines a three-point restraint between the anchorage 18,the latch plate 20, and the anchorage 24. Any other suitableconfigurations, such as alternative locations for the retractor assembly32, the latch plate 20, and the anchorage 24, may be used with thepresent invention.

Now with reference to FIG. 2, an isometric view of the seatbelt assembly12 is illustrated disassociated from the motor vehicle and showing theretractor assembly 32 in accordance with an exemplary embodiment. Theretractor assembly 32 includes a spool assembly 34 and a gas generator36 mounted to a common frame 38. The spool assembly 34 is connected withand stows the seatbelt webbing 14 of the shoulder belt portion 16,whereas the end of the lap belt portion 22 of the seatbelt webbing 14 isfixedly engaged with the anchorage point, for example, the frame 38 oranother portion of the motor vehicle such as the seat 10 (shown inFIG. 1) or floor pan.

Referring also to FIG. 3, the spool assembly 34 includes a belt spool 40that engages the shoulder belt portion 16 of the seatbelt webbing 14 androtates to wind-up or pay-out the seatbelt webbing 14. A torsional“clock” or “motor” type spring is carried within a spring end cap 42 androtationally biases the belt spool 40 to retract the seatbelt webbing14. The spool assembly 34 may further incorporate other spool controlmechanisms that are known in accordance with the prior art, includingpretensioners, inertia and webbing sensitive locking devices, torsionbar load limiters, or other belt control devices. “Spool controlsystems” referred to in this specification may include any system thatcontrols the rotational movement of a webbing spool, thus controllingthe extraction and retraction of seatbelt webbing. One such spoolcontrol system is a motor-assisted retractor. Spool locking devicestypically incorporate an inertia sensitive element, such as a rollingball or pendulum, and cause a sprocket of the spool to be engaged toprevent further withdrawing of the seatbelt webbing 14 from the beltspool 40. Webbing sensitive locking devices sense rapid pay-out ofseatbelt webbing 14 to lock the retractor assembly 32. Variouselectronic sensing mechanisms that detect the withdrawal of seatbeltwebbing 14 and/or the connection of the latch plate 20 to the seatbeltbuckle 28 may also be incorporated into the retractor assembly 32.

During normal operation of the vehicle, the retractor assembly 32 allowspay-out of seatbelt webbing 14 to give the occupant a certain amount offreedom of movement. However, if an impact or a potential impactsituation is detected, the retractor assembly 32 is locked to preventpay-out and to secure the occupant in the seat 10. For example, if thevehicle decelerates at a predetermined rate or if the brakes areactuated with a predetermined force, then the retractor assembly 32 islocked. Due in part to the free pay-out of the seatbelt webbing 14, theseatbelt assembly 12 often develops slack during normal use.

FIG. 4 provides a cut-away illustration of a pretensioner system 44 inaccordance with an exemplary embodiment. Referring to FIGS. 3-4, inparticular, the retractor assembly 32 further incorporates thepretensioner system 44 operatively connected to the spool assembly 34and operable to rotate the belt spool 40 for pretensioning. As known tothose of skill in the art, a retractor pretensioner winds seatbeltwebbing into a more taught condition against the occupant at the initialstages of a detected vehicle impact. This is provided to reduce forwardmotion or excursion of the occupant in response to the decelerationforces of a vehicle impact or rollover.

The pretensioner system 44 includes a pretensioner tube 52 incommunication with the gas generator 36. The gas generator 36 is used toprovide expanding gas in response to a firing signal. As is known in theart, for example, the vehicle includes a sensor array sending a signalindicative of an emergency event such as an impact event, crash, orrollover. The vehicle sensor may be a specific impact sensor, or may bea traditional vehicle sensor (e.g. a longitudinal or lateralacceleration sensor) or otherwise part of a control system having asuite of multiple sensors. Any other impact sensor that is or will beknown to those skilled in the art may also be readily employed inconjunction with the seatbelt assembly 12 of present invention. Anelectronic control unit such as a central processing unit (CPU) or othercontroller receives a signal and controls the seatbelt assembly 12 torespond by tightening the seatbelt webbing 14 of the vehicle (e.g. viaactivation of a pretensioner).

As will be discussed in further detail below, the pretensioner tube 52has a pretensioner rod 53, e.g., a plastically deformable polymer rod,disposed therein that has an elongate shape and is flexible within thetube 52. More specifically and as will be discussed in further detailbelow, the pretensioner rod 53, when disposed outside of thepretensioner tube 52 prior to insertion therein, has a generallystraight shape, and when inserted into the tube 52 it will bend and flexin accordance with the tortuous shape of the tube 52.

Turning now to the retractor assembly 32, the retractor assembly 32includes the spool assembly 34 mounted to the common frame 38, asdescribed above. More particularly, the spool assembly 34 will rotaterelative to the common frame 38 to wind the seatbelt webbing 14 attachedto the spool assembly 34. The common frame 38 includes a housing 54 forhousing the components of the pretensioner system 44.

The spool assembly 34 includes a sprocket 56 that is disposed within thehousing 54. The sprocket 56 is attached to the belt spool 40. Rotationof the sprocket 56 will cause the attached belt spool 40 to rotate towind the seatbelt webbing 14 that is attached to the belt spool 40.

FIG. 5 provides a side cut-away illustration of the pretensioner rod 53and a stopper 55 in accordance with an exemplary embodiment. FIGS.13A-13E provide cross-sectional views of various embodiments of thepretensioner rod 53 illustrated in FIG. 5 along line 13-13. As shown inFIGS. 5 and 13A-13E, the pretensioner rod 53 has a generally circularcross-section in one form. In another approach, the pretensioner rod 53could have a non-circular cross-section, such as a generally rectangularcross-section, generally triangular cross-section, or other polygonalcross-section that allows the pretensioner rod 53 to be inserted intothe pretensioner tube 52 (shown in FIG. 4) and adapt to the tortuousshape of the pretensioner tube 52 when inserted. For purposes ofdiscussion, the pretensioner rod 53 will be discussed as having agenerally circular cross-section

As illustrated and as discussed above, the pretensioner rod 53, whendisposed outside of the pretensioner tube 52, has a generally straightshape and extends in a longitudinal direction 200 from a proximal endportion 202 to a distal end portion 204. The proximal end portion 202 isdisposed towards the gas generator 36 (shown in FIG. 10) when thepretensioner rod 53 is installed within the pretensioner system 44. Inan exemplary embodiment, the pretensioner tube 52 has a cross-sectionthat varies along its length to define a non-recessed portion 206 and arecessed portion 208 that defines a recess 210. In one example and asillustrated in FIGS. 5 and 13D, the recess 210 is configured as a groove212, e.g., U-shaped groove with sidewalls 214. In another example and asillustrated in FIG. 13A, the recessed portion 208 has a recessed ruledsurface 214, e.g., substantially flat surface, that defines the recess210. Non-limiting alternative examples of different forms of the recess210 are illustrated in FIGS. 13B-13C and 13E.

Referring to FIG. 5, in an exemplary embodiment, the recessed portion208 extends along a majority of the overall length of the pretensionerrod 53 from the proximal end portion 202 to and including the distal endportion 204. As illustrated, the proximal end portion 202 includes thenon-recessed portion 206 in which the recess 210 terminates at adistal-most section of the non-recessed portion 206. As will bediscussed in further detail below and as illustrated in FIGS. 5 and13A-13E, the non-recessed portion 206 of the pretensioner rod 53 has adiameter, cross-sectional dimension, and/or perimeter greater than therecessed portion 208. In an exemplary embodiment, the non-recessedportion 206 has a length L1 of from about 15 to about 25 mm, such asabout 20 mm and a width W1 of from about 4 to about 7 mm, and therecessed portion 208 has a length L2 of from about 60 to about 145 mmand a thickness W2 of from about 2.5 to about 8.0 mm.

In an exemplary embodiment, the pretensioner rod 53 also includes apositive feature 216, e.g., nub or post, extending proximally from theproximal end portion 202. The stopper 55 has a negative feature 218formed therein that receives the positive feature 216 to couple thestopper 55 to the proximal end portion 202 of the pretensioner rod 53.In one example, the negative feature 218 and the positive feature 216are sized such that the stopper 55 is compression fit, e.g.,interference fit, onto the positive feature 216 to fixedly couple thestopper 55 to the pretensioner rod 53. Other forms of coupling and/orfixing the stopper 55 to the positive feature 216 and/or the proximalend portion 202 may be used, such as, for example, an adhesive,mechanical means, or the like. As illustrated in FIG. 5, the positivefeature 218 can be configured as a blind hole 220. Alternatively and asillustrated in FIG. 6, the negative feature 220 can be configured as athrough-hole 222 with the positive feature 216 extending partially orfully therethrough.

In an exemplary embodiment, the pretensioner rod is made from a polymermaterial, which has a reduced weight relative to metallic ball drivingelements of other roto-pretensioners. The particular polymer materialcan be selected to fit the particular desires of the user. The polymermaterial is preferably one that has sufficient flexibility such that itcan bend and flex through the pretensioner tube 52 to allow for initialinstallation as well as in response to actuation by the gas generator36. The polymer material is preferably one that has sufficientpushability in response to actuation, such that the pretensioner rod 53will sufficiently transfer a load to a sprocket 56 of the pretensionersystem 44, thereby functioning as a driving element for causingpretensioning.

Further, in an exemplary embodiment, the pretensioner rod 53 is madefrom a polymer material that is plastically deformable. During and afteractuation, the pretensioner rod 53 will be become plastically deformedin response to actuation and contact with other components (e.g., thesprocket 56) of the pretensioner system 44. As will be discussed infurther detail below, this plastic deformation will cause thepretensioner rod 53 to become locked, for example, in the sprocket 56 toprevent or limit payback of the pretensioner rod 53 without beingcompletely dependent on maintained pressure in the system.

In one approach, the pretensioner rod 53 is made from a nylonthermoplastic material. The pretensioner rod 53 could also be made froma aliphatic polyamide thermoplastic material. In another approach, thepretensioner rod 53 could be made from a similar thermoplastic material,such as an acetal material or polypropylene material.

With reference to FIGS. 7-9, the sprocket 56 has a general annular shapethat defines an internal aperture 76. The sprocket 56 further defines aplurality of inward extending teeth 78 that extend into the aperture 76.The teeth 78 are sized and configured to correspond to recesses ordepressions that are defined on an external surface of the belt spool 40(shown in FIG. 3) to connect the sprocket 56 to the belt spool 40 suchthat they are rotationally coupled. In another approach, the internalaperture 76 could include a single tooth or protrusion to rotationallycouple the sprocket 56 to the belt spool 40.

The sprocket 56 includes an annular body portion 80 and a flange portion82 that projects radially from the base of the annular body portion 80.The sprocket 56 further includes a plurality of vanes 84 that eachproject radially from the annular body portion 80 as well aslongitudinally from the flange portion 82, such that vanes 82 extendbetween the annular body portion 80 and the flange portion 82.

The vanes 84 each have a generally triangular shape when viewed from thefront, with a base that tapers into a point 86 as the vane 84 extendsradially outward from the annular body portion 80. The particular widthand pitch of the vanes 84 can be selected as desired. The plurality ofvanes 84 combine to define cavities 88 that are disposed betweenadjacent vanes 84.

In one approach, each of the vanes 84 can have the same size and shapeand be uniformly distributed around the sprocket 56. In anotherapproach, the vanes 84 can have different sizes and/or be spaced atdifferent intervals. Adjusting the size and spacing of the vanes 84 canalter the amount of rotation and/or the rate of the rotation for thesprocket 84 when the pretensioner system 44 is activated. This variablesize and/or spacing is possible due to the actuation by the pretensionerrod 53 rather than by a series of similarly shaped balls. In apretensioner that uses a plurality of ball-shaped driving elements, thesize and spacing is preferably uniform to account for the predeterminedshape and size of the balls.

With reference once again to FIG. 4, the housing 54 further include aguide portion 90. The guide portion 90 is disposed within the housing 54similar to the sprocket 56. More particularly, the guide portion 90 isdisposed opposite the exit of the tube 52, and the sprocket 56 isdisposed between the guide portion 90 and the tube 52. Accordingly, thepretensioner rod 53 exiting the tube 52 will contact the sprocket 56prior to contacting the guide portion 90.

The guide 90 has a generally arcuate landing surface 92 that has aconcave shape toward the exit of the tube 52. In one approach, the arcof the surface 92 has a constant radius. Further, the center point ofthe radius of the arc is aligned with the rotational axis of thesprocket 56, such that the radial spacing between the surface 92 and thesprocket 56 is consistent along the length of the surface 92. In anotherapproach, the center point of the radius of the surface 92 could beoffset from sprocket axis, such that the radial spacing between thesurface 92 and the outer diameter of the sprocket 56 will vary atdifferent points along the surface 92.

The surface 92 includes a first end 96 and second end 98. The first end96 is disposed opposite the exit of the tube 52 such that thepretensioner rod 53 would engage the first end 96 prior to the secondend 98 after exiting the tube 52 and passing the sprocket 56.

The housing 54 further defines an overflow cavity 100 that is disposedopposite the guide 90. The overflow cavity 100 is also disposed adjacentthe curvature of the tube 52, and the sprocket 56 is disposed betweenthe guide 90 and the overflow cavity 100. Accordingly, an intermediateportion 101 of the guide 90 is diametrically opposite the overflowcavity 100 across the sprocket 56.

The overflow cavity 100 is sized and configured to allow a portion thepretensioner rod 53 to be received therein during actuation ofpretensioner system 44, if necessary. For example, after thepretensioner rod 53 has exited the tube 52 it will contact the guide 90and be directed in an arcuate path corresponding to the guide 90, suchthat the pretensioner rod 53 is ultimately directed toward the overflowcavity 100. The pretensioner rod 53 can extend into the overflow cavity100, and can further be guided along the curvature of the tube 52 thatis adjacent the overflow cavity 100. However, it will be appreciatedthat the pretensioner rod 53 may not necessarily travel far enoughduring actuation to ultimately reach the overflow cavity 100.

As described above, the retractor assembly 32 includes the gas generator36 that provides expanding gas in response to a firing signal. Theexpanding gas causes an increase in pressure within the tube 52, whichultimately causes the pretensioner rod 53 to be forced away from the gasgenerator 36, through the tube 52, and pass the exit into the sprocket56 for pretensioning.

More particularly, as shown in FIG. 10, the pretensioner tube 52includes a piston or seal member 102. The seal member 102 can have aspherical shape with a spherical outer surface, in one approach. Inanother approach, the seal member 102 can have a generally cylindricalshape with a cylindrical outer surface. The seal member 102 is slidablydisposed within the tube 52 and is operable to drive the pretensionerrod 53 along an actuating direction or path A. As will be understood bythose of skill in the art, the seal member 102 may be press-fitted orotherwise fitted inside the tube 52.

As shown in FIG. 10, the seal member 102 defines a proximal end 106spaced from the gas generator 36 so as to define a gas chamber 108therebetween. The seal member 102 defines a distal end 110 directedtoward the stopper 55 and the pretensioner rod 53.

The stopper 55 is preferably made from aluminum, but could be made fromanother suitable material of sufficient strength, such as steel, othermetal or metal alloy, or reinforced plastic with the seal member 102being generally softer such that it can provide the described sealingabilities. In an exemplary embodiment, the stopper 55 has an outerperimeter that substantially matches the perimeter of the non-recessedportion 206. The stopper 55 is adjacent the distal end 110 of the sealmember 102 and abuts the non-recessed portion 206 of the pretensionerrod 53.

The seal member 102 and the stopper 55 cooperate to transfer the energyfrom the increased pressure in the gas chamber 108 to the pretensionerrod 53. The pretensioner rod 53, in order to travel through the tube 52and flex according to the curvature of the tube 52, is sized slightlysmaller than the width of the tube 52. Thus, without the seal member102, gas from the gas generator 36 would flow past the pretensioner rod53 in the space defined between the pretensioner rod 53 and the tube 52.

The seal member 102 defines a generally elastic structure, and may becomposed of various materials known in the art, such as any suitableplastic or polymer (e.g., polyester, rubber, thermoplastic, or otherelastic or deformable material). Moreover, the seal member 102 may bedie cast, forged, or molded from metal, plastic, or other suitablematerial. In one embodiment, the seal member 102 is formed using atwo-cavity injection molding process. The generally elastic structureallows the shape of the seal member 102 to change slightly in responseto pressure, thereby improving the sealing that it provides.

Referring to FIGS. 10-11, in operation, the gas generator 36 producesexpanding gas that pressurizes the gas chamber 108, thereby enabling theseal member 102 to forcibly drive the pretensioner rod 53 along theactuation path A. As the pretensioner rod 53 is driven through the tube52, it engages the sprocket 56. More particularly, the pretensioner rod53 engages the vanes 84 of the sprocket 56. Engagement of thepretensioner rod 53 with the sprocket 56 as the pretensioner rod 53 isdriven by expanding gas in the direction of arrow A causes the beltspool 40 (shown in FIG. 3) to rotate, which in turn providespretensioning.

Activation of the gas generator 36 enables the seal member 102 to resistgas leakage. As previously mentioned, the seal member 102 is composed ofa relatively elastic material. Therefore, pressurized gas within the gaschamber 108 causes the proximal end 106 of the seal member 102 toexpand, which helps prevent gas from escaping past the seal member 102.

In addition, backpressure generated from the pretensioner rod 53 causesthe seal member 102 to expand circumferentially outward due tocompression of the seal member 102 against the stopper 55 and thepretensioner rod 53. The pretensioner rod 53 undergoes resistance as itengages the sprocket 56 during actuation, thereby generatingbackpressure on the stopper 55 and the seal member 102. Thecircumferential expansion of the seal member 102 provides a tightenedseal between the outer surface of the seal member 102 and the inner wallof the pretensioner tube 52. Accordingly, the seal member 102 of thepresent invention is operable to retain a high seal pressure as well asmaintain residual gas pressure within the tube 52.

During pretensioning of the seatbelt there can be a side-effect known aspayback, where the tension on the seatbelt caused by the occupant duringan event triggering pretensioning can rotate the spool in a directionopposite the pretensioning rotation. This rotation is transferred to thesprocket 56 and the driving elements, causing the driving elements totravel in the reverse direction within the tube 52. Payback can becounteracted by maintaining pressure in the tube 52, but this requiresthe gas generator 36 to fire for a longer period and additionalpropellant.

However, in an exemplary embodiment, the pretensioner system 44described herein includes features configured to counteract the abovedescribed payback side-effect as an alternative to or in addition tomaintained gas pressure. As described above, the pretensioner rod 53 ispreferably made of a plastically deformable material, such as a polymer.

During actuation of the pretensioner system 44, the pretensioner rod 53exits the tube 52 and contacts the vanes 84 of the sprocket 56, causingthe sprocket 56 to rotate. As the pretensioner rod 53 continues past thesprocket 56 causing it to rotate, additional ones of vanes 84 willcontact the side of the pretensioner rod 53, causing the pretensionerrod 53 to be compressed and deformed plastically in the area ofinterference between the vanes 84 and the pretensioner rod 53. Thiscompression will also cause the pretensioner rod 53 to be compressedagainst the guide 90, creating a press-fit configuration of thepretensioner rod 53 between the sprocket 56 and the guide 90.

Additionally, the pretensioner rod 53 and guide 90 may be made frommaterials that will weld together at the end of the pretensioningstroke. For example, the materials of the pretensioner rod 53 and guide90 may be selected such that heat generated from the friction betweenthe pretensioner rod 53 and the guide 90 will cause the pretensioner rod53 and guide 90 to become welded together along an interface W where theguide 90 and rod 53 contact each other. Once the pretensioner rod 53 andguide 90 are welded together, the pretensioner rod 53 will become lockedand prevented or substantially limited from traveling back into the tube52. The plastic deformation of the pretensioner rod 53 caused by thevanes 84 will prevent or substantially limit the sprocket 56 fromrotating in the opposite direction, thereby preventing or substantiallylimiting payback.

The welding results from the relatively high heat and pressure generatedby the system during actuation. For the pretensioner rod 53 and guide 90to weld, the materials used for each are preferably in the same family.For example, if the guide 90 is nylon, then the pretensioner rod 53 ispreferably nylon. Similarly, if the guide 90 is acetal, then thepretensioner rod 53 is preferably acetal. If the guide 90 ispolypropylene, then the pretensioner rod 53 is polypropylene. It will beappreciated that other materials that will weld together under high heatand pressure could also be used. Moreover, it will be appreciated thatsome different types of materials can weld together.

Another side-effect that can occur during pretensioning is known as alow-resistance condition. This can occur when there is a relativelylarge portion of the seatbelt webbing that can be taken up or wound bythe spool in response to actuating the pretensioner. For example, ifthere was extra slack in the seatbelt, this slack would be taken up andwound with lower resistance because it would not be acting on theoccupant until the slack was taken up. In a low resistance condition,the backpressure of the driving elements is reduced. Reducedbackpressure can result in a reduced ability of the sealing element toexpand circumferentially against the inner wall surface of the tube inresponse to the backpressure. This can occur for any type of piston orseal that is configured to expand circumferentially in response tobackpressure as part of its sealing process.

With reference to FIGS. 4, 11, and 14-17, to address the side-effect ofa low-resistance condition of the pretensioner system 44, in anexemplary embodiment, the tube 52 includes a projection 120 extendingwithin the tube 52 near an end of the tube 52 to form constrictionportion 130 proximate to where the pretensioner rod 53 exits, therebyreducing the cross-sectional area of the tube 52 in a distinct location.That is, the opening diameter, width, or dimension(s) of theconstriction portion 130 is smaller than the diameter, width, ordimension(s) of adjacent portions of the tube 52 portions, such as, forexample, the portions of the tube 52 that are upstream from theconstriction portion 130.

As will be discussed in further detail below, the recess 210 is alignedwith the projection 120 along the actuating direction or path A suchthat during actuation and/or pretensioning, the recessed portion 208 ofthe pretensioner rod 53 is not obstructed by the projection 120.Moreover, the constriction portion 130 is sized such that there isenough space that at least the recessed portion 208 of the pretensionerrod 53 can travel past the constriction portion 130, but the stopper 55and seal member 102 will be blocked from travelling past theconstriction portion 130. When the stopper 55 and the seal member 102are blocked from advancing past the constriction portion 130, theconstriction portion 130 provides additional backpressure. Accordingly,the seal member 102 will circumferentially or radially expand inresponse to this backpressure, thereby providing an improved seal inlow-resistance conditions. This improved sealing will prevent or limitthe potential for gas to escape from the tube in low-resistanceconditions.

The projection 120 defining the constriction portion 130 can be formedin a variety of ways and have a variety of shapes while providing theabove described functionality. In one approach, shown in FIG. 14, theprojection 120 is in the form of a crimp or bump 132 in the tube 52,such that the sidewall of the tube 52 maintains substantially the samethickness. The bump 132 is integrally formed with the tube as amonolithic structure, at least in the area of the constriction portion130. Put another way, the bump 132 is not a separate component ormaterial attached to the tube 52. The bump 132 protrudes into the tube52, and has a corresponding depression 134 on an outer surface of thetube 52 (facing the overflow cavity 100, for example). The bump 132 hasa convex shape within the tube 52 and the depression 134 has acorresponding concave shape facing the overflow cavity 100.

In another approach, shown in FIG. 15, the projection 120 could be inthe form of an increased thickness portion 138 that is integral with thetube 52. This is similar to the bump 132, but does not have acorresponding depression on outer surface of the tube 52.

In another approach, shown in FIG. 16, the projection 120 is in the forma separate piece or crescent 136 that is attached to the tube 52 withinthe tube 52. The crescent 136 a, 136 b, or 136 c can be attached viawelding, adhesive, mechanical fasteners, or the like.

In another approach, shown in FIG. 17, the projection 120 could be inthe form of a plate 140 that is inserted through an opening 142 formedin the sidewall of the tube 52. The plate 140 is removably insertedthrough the opening 142 and secured to the tube 52 via known securementmechanisms. In another approach, the plate 140 can be fixedly securedafter insertion through the opening 142. The use of the plate 140 allowsfor different shapes and sizes and materials to be easily selected andinstalled, if desired.

In the above approaches, the projection 120 with the recess 210 of thepretensioner rod 53 aligned therewith may be disposed along an inboardportion of the tube 52 as illustrated in FIG. 4, or alternatively, maybe disposed along an outboard portion of the tube 52 as illustrated inFIG. 12. Advantageously, in an exemplary embodiment, disposition of theprojection 120 on the inboard portion of the tube 52 facilitates thepretensioner rod 53 sliding across the outboard portion of the tube 52during travel. The centrifugal force of the pretensioner rod 53 as ittravels through the tube 52 will tend to force the pretensioner rod 53toward the outboard portion of the tube 52, so locating the projection120 on the inboard portion helps reduces the potential for theconstriction portion 130 to add resistance to the pretensioner rod 53.Alternatively and advantageously, in an exemplary embodiment,disposition of the projection 120 on the outboard portion of the tube 52facilitates the sprocket 56 engaging the fully or solid side of thepretensioner rod 53 (e.g., sprocket 56 engaging side of the pretensionerrod 53 opposite the recess 210) during actuation to facilitate lockingthe pretensioner rod 53 with the sprocket 56 to prevent or reduce anytranslation of the pretensioner rod 53 in a direction opposite theactuating direction or path A.

As described above, the pretensioner rod 53 has the non-recessed portion206 at its proximal end portion 202, where the non-recessed portion 206has a larger diameter or cross-sectional dimension(s) than the recessedportion 208. In one approach, the non-recessed portion 206 has adiameter or cross-sectional dimension(s) that is larger than the widthor cross-sectional dimension(s) of the tube 52 at the constrictionportion 130. Accordingly, with the non-recessed portion 206 disposedupstream of the constriction portion 130, the constriction portion 130will prevent the non-recessed portion 206 from passing.

In another approach, the non-recessed portion 206 can be smaller thanthe width or cross-sectional dimension(s) of the tube 52 at theconstriction portion 130. With the non-recessed portion 206 being smallenough to pass the constriction potion 130, it can pass beyond theconstriction portion 130.

FIG. 18 provides a cut-away illustration of a pretensioner system 144 inaccordance with another exemplary embodiment. The pretensioner system144 shown in FIG. 18 is similarly configured to and operates asdescribed above in relation to the pretensioner system 44 shown in FIG.4 including the housing 54, the gas generator 36, the sprocket 56, andthe guide portion 90, but with the exceptions that the pretensioner tube152 has the projection 120 on the outboard portion of the tube 152 forinterfacing with a pretensioner rod 153 disposed within the tube 152. Aswill be discussed in further detail below, the pretensioner rod 153,e.g., a plastically deformable polymer rod, has an elongate shape and isflexible within the tube 152 and is similarly configured to and operatesas described above in relation to the pretensioner rod 53 shown in FIGS.4-6 but with the exception that the pretensioner rod 153 includes arecessed section 250 to further facilitate bending of the pretensionerrod 153 through the tube 152 during translation towards the sprocket 56.

In particular and with reference also to FIGS. 19-21D, the pretensionerrod 153 when disposed outside of the pretensioner tube 152 prior toinsertion therein, has a generally straight shape, and when insertedinto the tube 152 it will bend and flex in accordance with the tortuousshape of the tube 152. As shown, the pretensioner rod 153 has agenerally circular cross-section in one form. In another approach, thepretensioner rod 153 could have a non-circular cross-section, such as agenerally rectangular cross-section, generally triangular cross-section,or other polygonal cross-section that allows the pretensioner rod 153 tobe inserted into the pretensioner tube 152 and adapt to the tortuousshape of the pretensioner tube 152 when inserted. For purposes ofdiscussion, the pretensioner rod 153 will be discussed as having agenerally circular cross-section.

As illustrated and as discussed above, the pretensioner rod 153, whendisposed outside of the pretensioner tube 152, has a generally straightshape and extends in the longitudinal direction 200 from its proximalend portion 202 to its distal end portion 204. The proximal end portion202 is disposed towards the gas generator 36 when the pretensioner rod153 is installed within the pretensioner system 144. In an exemplaryembodiment, the pretensioner tube 152 has a cross-section that variesalong its length to define the non-recessed portion 206 and the recessedportion 208 that defines the recess 210 as discussed above in relationto the pretensioner rod 53 shown in FIGS. 5-6.

On a side opposite the recessed portion 208 is the recessed section 250that defines a recess 252 and that extends in the longitudinal direction200. In an exemplary embodiment, the cross-section of the pretensionertube 152 varies along its length to define a non-recessed section 254 atthe distal end portion 204 and the recessed section 250 extends from thenon-recessed section 254 to a proximal-most end of the proximal endportion 202 to define the recess 252. As such, the recessed section 250extends along the majority of the overall length of the pretensioner rod153. In an exemplary embodiment, it has been found that by not extendingthe recess 252 through the distal end portion 204, the distal endportion 204 has a relatively larger or fuller cross-sectional area forengaging the sprocket 56 during translation, thereby reducing the amountof stripping of the pretensioner rod 153 which can occur at firstcontact with the sprocket 56, thereby increasing performance of thepretensioner system 144. Moreover, it has been found that by not havingthe recess/groove 210 extend through the proximal end portion 202, theproximal end portion 202 has a relatively larger or fullercross-sectional area for the stopper 55 to contact to reduce the amountof initial compression on the pretensioner rod 153 during actuation ofthe gas generator 36, thereby increasing performance of the pretensionersystem 144.

In an exemplary embodiment, the recessed section 250 is sized such thata thickness (indicated by double headed arrow 256) of the pretensionerrod 153 defined normal to the recessed section 250 is less than a width(indicated by double headed arrow 258) of the pretensioning rod definednormal to the thickness to facilitate bending of the pretensioner rod153 through the pretensioner tube 152 during translation to the sprocket56. Without being limited by theory, it is believed that the recessedsection 250 helps reduce the section modulus across the thickness 256 ofthe pretensioner rod 153 to allow the pretensioner rod 153 to bend moreeasily across its thickness 256. Further, it is believed that thisreduction in section modulus helps prevent twisting of the pretensionerrod 153 and reduce friction as the rod 153 is being advanced through thepretensioner tube 152 during translation, thereby increasing performanceof the pretensioner system 144. Moreover, the recessed section 250facilitates insertion of the pretensioner rod 153 into the pretensionersystem 144 during assembly due to its reduced cross-sectional area. Inan exemplary embodiment, the non-recessed section 254 has a length L10of from about 15 to about 25 mm, such as about 20 mm; the recessedsection 250 has a length L20 of from about 60 to about 145 mm; thethickness 256 of the pretensioner rod 153 is, for example at theproximal end portion 202, from about 2.5 to about 7 mm; and the width258 of the pretensioner rod 153 is, for example at the proximal endportion 202, from about 4 to about 8 mm.

In an exemplary embodiment, when the pretensioner rod 153 is disposedoutside of the pretensioner tube 152, the recessed section 250 has asubstantially flat, planar surface defining the recess 252. In anotherexample, the recessed section 250 has a recessed ruled surface thatdefines the recess 252. Non-limiting alternative forms of the recess 252may also be used.

In an exemplary embodiment, the pretensioner rod 153 may include achamfer 260 at its distal end portion 204. The chamfer 260 mayadvantageously be positioned on the same side as the recess 210 to helpreduce the force required to advance the pretensioner rod 153 past theprojection 120 so as to minimize or prevent the pretensioner rod 153from being obstructed by the projection 120. Alternatively, the chamfer260 may be positioned on the side opposite the recess 210 as illustratedin FIGS. 5-6.

In an exemplary embodiment, the pretensioner rod 153 also includes apositive feature 216, e.g., nub or post, extending proximally from theproximal end portion 202. A stopper 55 is configured to receive thepositive feature 216 to couple the stopper 55 to the proximal endportion 202 of the pretensioner rod 153 as discussed above in relationto the pretensioner rod 53 shown in FIGS. 5-6.

As a person skilled in the art will readily appreciate, the abovedescription is meant as an illustration of the implementation of theprinciples of this invention. This description is not intended to limitthe scope or application of this invention in that the invention issusceptible to modification, variation, and change, without departingfrom the spirit of this invention as defined in the following claims.

The invention claimed is:
 1. A seatbelt pretensioning retractor assemblyfor use in a passenger vehicle, the seatbelt pretensioning retractorassembly comprising: a housing adapted for being mounted to a vehiclestructure and having an interior cavity; a tube having an arcuate andcurved shape having a first end for fluid communication with a gasgenerator and a second end in fluid communication with the interiorcavity of the housing; a sprocket rotatably mounted to the housing andfixedly coupled to a spindle adapted for taking up seatbelt webbingduring pretensioning, wherein the sprocket has a plurality of vanes; adriving element comprising a plastically deformable polymer rodconfigured to extend in a longitudinal direction and having a recessedportion defining a recess that extends generally in the longitudinaldirection, wherein the plastically deformable polymer rod is disposedwithin the tube and is translatable through the tube in a firstdirection toward the sprocket in response to an actuation by the gasgenerator; a stopper coupled to an end portion of the plasticallydeformable polymer rod; and a seal member disposed between the gasgenerator and the stopper, wherein the tube includes a projectionextending within the tube adjacent to the exit to define a constrictionportion that has an opening dimension smaller than an inside dimensionof adjacent portions of the tube, and wherein the recess is aligned withthe projection in the first direction and the constriction portion issized to permit the recessed portion of the plastically deformablepolymer rod to pass therethrough while preventing the stopper frompassing therethrough.
 2. The seatbelt pretensioning retractor assemblyof claim 1, wherein the recess is in a form of a groove defined by therecessed portion.
 3. The seatbelt pretensioning retractor assembly ofclaim 1, wherein the recessed portion has a recessed ruled surface thatdefines the recess.
 4. The seatbelt pretensioning retractor assembly ofclaim 1, wherein the plastically deformable polymer rod has a proximalend portion that is disposed towards the gas generator and a distal endportion that is opposite the proximal end portion, and wherein thestopper is coupled to the proximal end portion and the recessed portionextends distally from the proximal end portion to and includes thedistal end portion.
 5. The seatbelt pretensioning retractor assembly ofclaim 4, wherein the proximal end portion comprises a non-recessedportion that has a diameter, cross-sectional dimension, and/or perimetergreater than the recessed portion.
 6. The seatbelt pretensioningretractor assembly of claim 5, wherein the stopper abuts thenon-recessed portion and has an outer perimeter that substantiallymatches the perimeter the non-recessed portion.
 7. The seatbeltpretensioning retractor assembly of claim 4, wherein the plasticallydeformable polymer rod and the stopper are fixedly couple together by apositive feature extending generally in the longitudinal directionreceived by a negative feature.
 8. The seatbelt pretensioning retractorassembly of claim 1, wherein the plastically deformable polymer rod hasa recessed section extending in the longitudinal direction on a sideopposite the recessed portion.
 9. The seatbelt pretensioning retractorassembly of claim 1, wherein the projection is integrally formed withthe tube.
 10. The seatbelt pretensioning retractor assembly of claim 9,wherein the projection is in a form of a protrusion in a sidewall of thetube.
 11. The seatbelt pretensioning retractor assembly of claim 9,wherein the projection is in a form of a crimp in a sidewall of thetube.
 12. The seatbelt pretensioning retractor assembly of claim 9,wherein the constriction portion and the adjacent portions of the tubeform a monolithic structure.
 13. The seatbelt pretensioning retractorassembly of claim 1, wherein the projection is in a form of a separateprojection member fixedly mounted to a sidewall of the tube.
 14. Theseatbelt pretensioning retractor assembly of claim 1, wherein theprojection comprises a plate inserted through a hole defined in asidewall of the tube.
 15. The seatbelt pretensioning retractor assemblyof claim 1, wherein the projection and the recess are located along aninboard portion of the tube.
 16. The seatbelt pretensioning retractorassembly of claim 1, wherein the projection and the recess are locatedalong an outboard portion of the tube.
 17. The seatbelt pretensioningretractor assembly of claim 1, wherein the stopper is a circumferentialshape that generally matches the internal circumferential shape of thetube.
 18. The seatbelt pretensioning retractor assembly of claim 1,wherein the seal member expands circumferentially outward in response tobackpressure from the constriction portion during the actuation of thegas generator.
 19. The seatbelt pretensioning retractor assembly ofclaim 1, wherein the housing has a guide portion, and wherein theplastically deformable polymer rod is locked against translation in asecond direction that is opposite the first direction after theplastically deformable polymer rod has engaged the sprocket to providepretensioning and/or the plastically deformable polymer rod becomeslocked against translation in the second direction that is opposite thefirst direction during pretensioning due to welding between theplastically deformable polymer rod and the guide portion.
 20. A seatbeltpretensioning retractor assembly for use in a passenger vehicle, theseatbelt pretensioning retractor assembly comprising: a housing adaptedfor being mounted to a vehicle structure and having an interior cavity;a tube having an arcuate and curved shape having a first end for fluidcommunication with a gas generator and a second end in fluidcommunication with the interior cavity of the housing; a sprocketrotatably mounted to the housing and fixedly coupled to a spindleadapted for taking up seatbelt webbing during pretensioning, wherein thesprocket has a plurality of vanes; a driving element comprising aplastically deformable polymer rod configured to extend in alongitudinal direction and having a recessed portion defining a recessthat extends generally in the longitudinal direction and a recessedsection extending in the longitudinal direction on a side opposite therecessed portion, wherein the plastically deformable polymer rod isdisposed within the tube and is translatable through the tube in a firstdirection toward the sprocket in response to an actuation by the gasgenerator; and a seal member disposed between the gas generator and theplastically deformable polymer rod, wherein the tube includes aprojection extending within the tube adjacent to the exit to define aconstriction portion that has an opening dimension smaller than aninside dimension of adjacent portions of the tube, wherein the recess isaligned with the projection in the first direction and the constrictionportion is sized to permit the recessed portion of the plasticallydeformable polymer rod to pass therethrough, and wherein the recessedsection is sized such that a thickness of the plastically deformablepolymer rod defined normal to the recessed section is less than a widthof the plastically deformable polymer rod defined normal to thethickness to facilitate bending of the plastically deformable polymerrod through the tube during translation in the first direction.